Performance Benefits of Extending the AFOV of PET Scanners

Long axial field-of-view (AFOV) PET scanners have valuable benefits for both clinical and research applications. Thus far, two of these scanners are currently operational in the US: the 194-cm uExplorer at UC Davis and the PennPET Explorer at the University of Pennsylvania. We had previously reported performance metrics and human imaging studies on the 64-cm PennPET Explorer and have recently completed extending the AFOV of the scanner to a 5-ring, 112-cm system. We extended the NEMA metrics to scanners longer than 65-cm and performed sensitivity, count rate, spatial resolution, and contrast recovery measurements on the 5-ring system. The sensitivity of the system was 104 kcps/MBq; the peak NEC measured with a 20×70 cm count rate phantom was 1.6 Mcps @ 39 kBq/cc; the axial spatial resolution degraded slightly for the 62° acceptance angle; and the contrast recovery did not degrade as a function of increased axial acceptance angle. Therefore, extending the axial length of the PennPET Explorer from 64 cm to 112 cm, while expanding the acceptance angle, resulted in gains in sensitivity and count rate with minimal degradations in spatial resolution and no degradation of contrast recovery.